DaveReidUK
July 13, 2025, 10:15:00 GMT
permalink Post: 11921168

Quote:

Originally Posted by Someone Somewhere

I suspect they thought that stating the switches had been replaced twice since the bulletin was published would dispel such concerns.

The replacement of the switches wasn't directly connected with their operation, but a by-product of replacement (for some other reason) of the throttle control module.

Air India didn't inspect the switches on board their 787s when the SB came out, so it's doubtful that they inspected those on the spare modules in stores.

Subjects: None

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DaveReidUK
July 13, 2025, 20:29:00 GMT
permalink Post: 11921564

Quote:

Originally Posted by Musician

Yes.
The ADS-B data collected by FR24 leave the aircraft at 172 knots ~~8 seconds~~ 4 seconds into the outage. Vr was 155 knots per the report. The preliminary report also says it crashed at 8⁰ nose-up attitude, which was after the "flare".
Please tell me how recoverable that is, with hypothetical 95% thrust on both engines 2 6 seconds later.

edit: reviewed fr24 data and adjusted time covered; I think it did decelerate to approximately 155 knots in 10 seconds, based on -3knots/second.

The ADS-B data ceased approximately 3 seconds before the APU auto start sequence commenced.

Beware of comparing the speeds from ADS-B, which are groundspeeds, with those from the report, which are IAS.

Subjects ADSB APU FlightRadar24 Preliminary Report

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DaveReidUK
July 14, 2025, 09:14:00 GMT
permalink Post: 11921939

Quote:

Originally Posted by GroundedSpanner

In the case of the B787, switch PN 4TL837-3D. Check those AC to ensure locking is OK, and if you do happen to find something odd, let us (the FAA) know.
No-one, has ever found anything wrong with any of those other switches, or there would be AD's.

The SB specifically states that the concern does not warrant an AD, and does not request the operator to report findings to the FAA.

Subjects Air Worthiness Directives FAA

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DaveReidUK
July 16, 2025, 08:44:00 GMT
permalink Post: 11923493

Quote:

Originally Posted by tdracer

Not trying to be part of the on-going hamster wheel. But the discussions regarding the odds of this being pilot suicide based on historical rates are missing a very critical statistical point.
Let's just assume that rate of commercial airliner crashes due to pilot suicide is 1 in 100 million departures. Simply put, that means that if you get on a commercial aircraft to fly from point A to point B, the historical odds are that there is a 1 in 100 million chance that your flight will crash due to an intentional suicidal pilot act. However, the historical odds say that the odds of your flight crashing for any reason are several million to one. Since the turn of the century, the fatal cash rate has been something around 1 in 5 million departures.
Now, we know for a fact that the Air India 787 crashed - hence the probability of a crash for this particular flight is not 1 in 5 million - it's ONE! That means the historical odds of this crash being due to an intentional act by a pilot (i.e. suicide) is ~5%, not one in 100 million (obviously a rough number, but you get the idea).

It's an unfortunate fact that most people simply don't understand Bayes' Theorem. PPRuNe posters are not immune.

Subjects: None

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DaveReidUK
July 16, 2025, 13:53:00 GMT
permalink Post: 11923721

Quote:

Originally Posted by 1stspotter

You might want to carefully read the complete SAIB. The FAA wanted to make sure the issue on some of the B737 switches does not exist on other Boeing made aircraft.
It is here. https://feitoffake.wordpress.com/202...787-explained/

I don't think it's me who is having trouble reading the SAIB.

It calls for the switches on any of the types mentioned to be replaced if found defective, and for the older type of switches on the 737 to be replaced whether defective or not.

Subjects FAA Special Airworthiness Information Bulletin

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DaveReidUK
July 17, 2025, 09:38:00 GMT
permalink Post: 11924226

Quote:

Originally Posted by tdracer

There are good, valid reasons for the ICAO accident investigation rules - and one of those rules says they'd don't release information until it is properly vetted and validated.

Strictly speaking, they are SARPs (Standards and Recommended Practices) for accident investigation, not rules.

Subjects ICAO

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DaveReidUK
July 17, 2025, 12:15:00 GMT
permalink Post: 11924321

Quote:

Originally Posted by Lazyload

For everyone interested in the fco switches, here\x92s a totally authoritative explanation. Fast forward to about 15 minute mark.

Transcript of the relevant part:

"The unit is designed with a spring-loaded action when it's pulled up. Its natural state wants to stay down at all times - that is one locking mechanism. The secondary locking mechanism is the gate - when the switch is pulled up and transitioned into its next position, it gets locked by the gate, or the detent, or the bridge (whatever you want to call it)."

Obviously the narrator doesn't mean that there are two independent locking mechanisms - it's the combined action of the spring and the detent that supplies the desired locking characteristics.

Interestingly, he goes on to say that it was the failure of the spring on a 737 switch that led to the SB being issued.

Subjects Fuel (All) Fuel Cutoff Switches Fuel Cutoff Switches (detent)

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DaveReidUK
July 17, 2025, 13:11:00 GMT
permalink Post: 11924350

Quote:

Originally Posted by 1stspotter

There is not a single report of a switch failure on any of B787 aircraft.

The history of aviation in general, and accident investigation in particular, is littered with instances of "Hey, that's never happened before ...".

Subjects: None

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DaveReidUK
July 17, 2025, 14:08:00 GMT
permalink Post: 11924395

Quote:

Originally Posted by DTA

The spring and gate/bridge together are the single mechanism that prevents uncommanded operation of the switch. Neither works without the other.

Exactly.

The mechanical interference between the fixed (lower) and moving (upper) parts of the switch depends on the spring force forcing the two parts to mesh:

Subjects: None

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DaveReidUK
July 17, 2025, 16:59:00 GMT
permalink Post: 11924486

Quote:

Originally Posted by 1stspotter

Mary Schiavo told a lot of utter nonsense on this crash. Someone should write an article about this lady.

I think you'll find no shortage of articles written about Ms Schiavo over the course of her illustrious career. The industry needs more like her.

Subjects: None

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DaveReidUK
July 17, 2025, 18:30:00 GMT
permalink Post: 11924532

Quote:

Originally Posted by ex FE Hoppy

And the FAA responded by issuing a notice that the switches are fine in response to the Indian report which brought up an unrelated issue as if to muddy the facts.

FAA confirms that they didn't certificate the 787 with potentially dangerous fuel control switches ...

Subjects FAA Fuel (All) Fuel Cutoff Switches

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DaveReidUK July 13, 2025, 10:15:00 GMT permalink Post: 11921168	Quote: Originally Posted by Someone Somewhere I suspect they thought that stating the switches had been replaced twice since the bulletin was published would dispel such concerns. The replacement of the switches wasn't directly connected with their operation, but a by-product of replacement (for some other reason) of the throttle control module. Air India didn't inspect the switches on board their 787s when the SB came out, so it's doubtful that they inspected those on the spare modules in stores. Subjects: None 3 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
DaveReidUK July 13, 2025, 20:29:00 GMT permalink Post: 11921564	Quote: Originally Posted by Musician Yes. The ADS-B data collected by FR24 leave the aircraft at 172 knots ~~8 seconds~~ 4 seconds into the outage. Vr was 155 knots per the report. The preliminary report also says it crashed at 8⁰ nose-up attitude, which was after the "flare". Please tell me how recoverable that is, with hypothetical 95% thrust on both engines 2 6 seconds later. edit: reviewed fr24 data and adjusted time covered; I think it did decelerate to approximately 155 knots in 10 seconds, based on -3knots/second. The ADS-B data ceased approximately 3 seconds before the APU auto start sequence commenced. Beware of comparing the speeds from ADS-B, which are groundspeeds, with those from the report, which are IAS. Subjects ADSB APU FlightRadar24 Preliminary Report Links are to this post in the relevant subject page so that this post can be seen in context. 4 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
DaveReidUK July 14, 2025, 09:14:00 GMT permalink Post: 11921939	Quote: Originally Posted by GroundedSpanner In the case of the B787, switch PN 4TL837-3D. Check those AC to ensure locking is OK, and if you do happen to find something odd, let us (the FAA) know. No-one, has ever found anything wrong with any of those other switches, or there would be AD's. The SB specifically states that the concern does not warrant an AD, and does not request the operator to report findings to the FAA. Subjects Air Worthiness Directives FAA Links are to this post in the relevant subject page so that this post can be seen in context. 1 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
DaveReidUK July 16, 2025, 08:44:00 GMT permalink Post: 11923493	Quote: Originally Posted by tdracer Not trying to be part of the on-going hamster wheel. But the discussions regarding the odds of this being pilot suicide based on historical rates are missing a very critical statistical point. Let's just assume that rate of commercial airliner crashes due to pilot suicide is 1 in 100 million departures. Simply put, that means that if you get on a commercial aircraft to fly from point A to point B, the historical odds are that there is a 1 in 100 million chance that your flight will crash due to an intentional suicidal pilot act. However, the historical odds say that the odds of your flight crashing for any reason are several million to one. Since the turn of the century, the fatal cash rate has been something around 1 in 5 million departures. Now, we know for a fact that the Air India 787 crashed - hence the probability of a crash for this particular flight is not 1 in 5 million - it's ONE! That means the historical odds of this crash being due to an intentional act by a pilot (i.e. suicide) is ~5%, not one in 100 million (obviously a rough number, but you get the idea). It's an unfortunate fact that most people simply don't understand Bayes' Theorem. PPRuNe posters are not immune. Subjects: None 5 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
DaveReidUK July 16, 2025, 13:53:00 GMT permalink Post: 11923721	Quote: Originally Posted by 1stspotter You might want to carefully read the complete SAIB. The FAA wanted to make sure the issue on some of the B737 switches does not exist on other Boeing made aircraft. It is here. https://feitoffake.wordpress.com/202...787-explained/ I don't think it's me who is having trouble reading the SAIB. It calls for the switches on any of the types mentioned to be replaced if found defective, and for the older type of switches on the 737 to be replaced whether defective or not. Subjects FAA Special Airworthiness Information Bulletin Links are to this post in the relevant subject page so that this post can be seen in context. 3 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
DaveReidUK July 17, 2025, 09:38:00 GMT permalink Post: 11924226	Quote: Originally Posted by tdracer There are good, valid reasons for the ICAO accident investigation rules - and one of those rules says they'd don't release information until it is properly vetted and validated. Strictly speaking, they are SARPs (Standards and Recommended Practices) for accident investigation, not rules. Subjects ICAO Links are to this post in the relevant subject page so that this post can be seen in context. 2 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
DaveReidUK July 17, 2025, 12:15:00 GMT permalink Post: 11924321	Quote: Originally Posted by Lazyload For everyone interested in the fco switches, here\x92s a totally authoritative explanation. Fast forward to about 15 minute mark. Transcript of the relevant part: "The unit is designed with a spring-loaded action when it's pulled up. Its natural state wants to stay down at all times - that is one locking mechanism. The secondary locking mechanism is the gate - when the switch is pulled up and transitioned into its next position, it gets locked by the gate, or the detent, or the bridge (whatever you want to call it)." Obviously the narrator doesn't mean that there are two independent locking mechanisms - it's the combined action of the spring and the detent that supplies the desired locking characteristics. Interestingly, he goes on to say that it was the failure of the spring on a 737 switch that led to the SB being issued. Subjects Fuel (All) Fuel Cutoff Switches Fuel Cutoff Switches (detent) Links are to this post in the relevant subject page so that this post can be seen in context. 2 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
DaveReidUK July 17, 2025, 13:11:00 GMT permalink Post: 11924350	Quote: Originally Posted by 1stspotter There is not a single report of a switch failure on any of B787 aircraft. The history of aviation in general, and accident investigation in particular, is littered with instances of "Hey, that's never happened before ...". Subjects: None 5 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
DaveReidUK July 17, 2025, 14:08:00 GMT permalink Post: 11924395	Quote: Originally Posted by DTA The spring and gate/bridge together are the single mechanism that prevents uncommanded operation of the switch. Neither works without the other. Exactly. The mechanical interference between the fixed (lower) and moving (upper) parts of the switch depends on the spring force forcing the two parts to mesh: Subjects: None 6 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
DaveReidUK July 17, 2025, 16:59:00 GMT permalink Post: 11924486	Quote: Originally Posted by 1stspotter Mary Schiavo told a lot of utter nonsense on this crash. Someone should write an article about this lady. I think you'll find no shortage of articles written about Ms Schiavo over the course of her illustrious career. The industry needs more like her. Subjects: None 1 recorded likes for this post. Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
DaveReidUK July 17, 2025, 18:30:00 GMT permalink Post: 11924532	Quote: Originally Posted by ex FE Hoppy And the FAA responded by issuing a notice that the switches are fine in response to the Indian report which brought up an unrelated issue as if to muddy the facts. FAA confirms that they didn't certificate the 787 with potentially dangerous fuel control switches ... Subjects FAA Fuel (All) Fuel Cutoff Switches Links are to this post in the relevant subject page so that this post can be seen in context. No recorded likes for this post (could be before pprune supported 'likes'). Reply to this quoting this original post. You need to be logged in. Not available on closed threads.

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